This invention relates generally to the steering of mirrors. More particularly the invention relates to a mechanical device which has been especially adapted to reflect and direct an image, beam or light ray with a mirror to describe a circular arc on a plane in a precise manner, or reflect and direct an image beam, or light ray with two mirrors to a point in space from a radial direction in a precise manner.
Heretofore and up to the present time, the steering of a mirror to reflect and direct an image, beam or light ray has involved manually or mechanically positioning the mirror in a manner such that the mirror reflects the image, beam or light ray according to the law of mirror reflection, viz.: the angle of incidence is equal to the angle of reflection. Accordingly, the angle between the incident and reflected beams is twice the angle of incidence, and the normal line to the plane of the mirror bisects this angle. The task of precisely directing a reflected beam involves positioning the mirror such that the normal to the mirror bisects the subtended angle between the source of the beam and the desired position of the beam.
Several disadvantages are inherent in the task of positioning a mirror to direct a reflected beam to a target. If done manually, the beam must be present, and the beam must be directed to the target by trial and error. If done mechanically, the subtended angle between the source and the target must be measured; the spatial position of the beam source and the target must be determined. The mirror must then be positioned so that the normal lies in the plane of the source and target, the normal must precisely bisect the angle subtended by the source and the target.